1. Field of the Invention
This invention relates to molding resins and more specifically it relates to molding resins based on acid copolymer/linear polyolefin/reinforcing fiber blends.
2. Description of the Prior Art
Copolymers of ethylene and methacrylic acid partially neutralized with sodium or zinc ions are tough molding resins with a combination of good tensile properties and excellent abrasion resistance. Their greatest deficiency is their low softening point which is displayed by a low heat deflection temperature (HDT). The low heat deflection temperature causes parts molded from ionomers to sag and warp when exposed to temperatures much above 40.degree.-50.degree. C.
Ionomers are routinely blended with glass fibers to give composites with higher heat deflection temperatures. However, large amounts of glass are needed to obtain significant increase in HDT's and these materials do not retain their toughness.
Glass reinforced linear high density polyethylene (HDPE) has a high heat distortion temperature but a low Izod impact strength.
Blends of HDPE with ionomers do not have significantly improved HDT values and the blends have a tendency to be incompatible and delaminate on injection molding.
U.S. Pat. No. 3,856,724 discloses reinforced thermoplastic compositions based upon a reinforcing agent such as glass fiber or alpha cellulose with a polyolefin such as polyethylene, polypropylene, polyisobutylene, etc. and a minor amount of an ionic hydrocarbon copolymer, such as an ethylene-methacrylic acid copolymer which has been reacted with an ionizable metal compound. It is disclosed that generally, the amount of the ionic hydrocarbon copolymer will be from about 0.05 to about 35 percent by weight and, preferably, from about 1 to about 30 percent by weight based on the weight of the reinforced thermoplastic composition.